As mobile devices such as smart phones have been increasingly used, the functions of the mobile devices have become diversified. In particular, the function of detecting a voice using a microphone mounted in the mobile device to perform voice call and video call functions is one of the natural user-device interfaces and is being utilized for various purposes. For example, services such as Siri of Apple or Now of Google provide convenience of interpreting a user's voice as a command and providing specific information or activating a function. In addition, most of the mobile devices are provided with a voice activation function which detects voice commands and activates mobile devices even when the mobile devices are deactivated to reduce power consumption.
For example, Korean Patent Publication No. 10-2001-0101923 of Qualcomm Incorporated (Nov. 15, 2001) (titled “Voice Activated Mobile Telephone Call Answerer) discloses a mobile telephone call answerer which is activated by a voice.
The microphone of the mobile device may be used to receive sound waves modulated from digital information, in addition to receiving a command or acquiring information using a human voice. Such a function may be performed using the microphone and an audio processing hardware device unlike the original functions of the microphone, and may be used to transmit additional information to a user's mobile device using a sound system, for example, an announcement system in a building or a sound wave transmission-dedicated speaker, and receive information through the microphone.
For example, Korean Patent Application No. 10-2013-0129934 (Oct. 30, 2013) filed by the same applicant as the applicant of the present application (titled “Method and System for Estimating Location of Mobile Terminal Using Sound System, and Sound System”) discloses technology for providing information to a mobile device using a microphone, etc.
In addition, there is an application which can deliver information to a mobile device using sound waves as a voice command for activating the mobile device which is deactivated (or in a standby state) to reduce power consumption, regardless of whether the mobile device is activated/deactivated.
However, to transmit sound waves modulated from digital information, uni-directional communication is normally used. In this case, in order for a user's mobile device to receive micro sound waves, corresponding information should be transmitted. Therefore, a sound system which transmits sound waves or a sound wave transmission-dedicated speaker should transmit sound waves continuously and repeatedly.
For example, Korean Patent Application No. 10-2013-0129951 (Oct. 30, 2013) (titled “Broadcasting Method and System Using Non-audible Sound and Mixer) discloses technology for transmitting sound waves repeatedly.
However, when sound waves are repeatedly transmitted and are treated as a voice command to activate a mobile device as described above, the mobile device of a user who is in a place to which the corresponding sound waves are transmitted is continuously activated and does not enter an deactivation state. This may cause serious battery loss and thus the technology for activating a mobile device using a voice may be a cause of degradation in the technology of sound waves for delivering digital information.
In addition, since the mobile device uses power of limited capacity such as a battery, there is always a demand for low-power-based technology.